1. Field of the Invention
The present invention relates generally to a controller, and more particularly relates to a control system for controlling an appliance, such as a gas-fired heating device.
2. Description of the Related Art
Gas-powered appliances typically have some control system included for controlling the operation of the appliance. In this context, a gas-powered appliance may be a water heater, a fireplace insert, or a furnace, for example. Also in this context, “gas-powered” typically means that natural gas or liquid propane gas is used as a primary fuel source. Current control systems used in gas-powered appliances are typically powered by a source external to the appliance, or take the form of a thermo-mechanical system, of which both approaches have certain disadvantages.
In this respect, appliances with external power sources may be difficult to use in certain situations due to availability and/or proximity of a suitable power source. Additionally, such systems typically do not function in the event of a power outage, which is undesirable. While a thermo-mechanical back-up control system may be included in such an appliance, that approach may be overly redundant and cost prohibitive in a commercial application.
Likewise, gas-powered appliances that employ thermo-mechanical controls, while not using an external power supply, can also have certain disadvantages. Such thermo-mechanical controls are typically inaccurate due to machining tolerances, mechanical hysteresis and the use of only a single temperature sensing location due to the impracticability of multiple sensor configurations.
In certain applications, gas-powered appliances might have a standing pilot ignition that can suffer certain disadvantages from being powered by an external power source. Further, gas-powered appliances with a standing ignition might also suffer certain disadvantages from having separate operating means for system start-up and temperature selection.
Based on the foregoing, alternative approaches may be desirable.